Background: Siblings of children with mental retardation and developmental disabilities (MR/DD) show higher rates of psychological distress. Almost all studies of this phenomenon have been conducted with Anglo families yet there is reason to believe that this effect may be more pronounced within Latino families. In the last three decades, the Latino population in the mainland United States has nearly quadrupled. Due to relatively high rates of Latino immigration and child-bearing as well as increased risk for disabilities, there will be more Latino children with MR/DD in the US and they will have more siblings. Specific Aims: The aims of this study are 1) to examine the mental health and psychosocial functioning of Latino siblings of children with MR/DD to determine whether they exhibit elevated rates of internalizing psychological and somatic symptoms, psychopathology, and impairment in school and social functioning, as compared to nonLatino siblings of children with MR/DD and comparison siblings of typical children, and 2) to examine the unique role of cultural factors in the prediction of sibling mental health, psychosocial functioning, sibling relationship quality, and sibling family obligations. We hypothesize that after controlling for sociodemographic variables, Latino siblings of children with MR/DD will experience higher rates of internalizing psychological and somatic symptoms and psychopathology (i.e., anxiety and depressive disorders), and that these will be associated with more school and social impairment. We also hypothesize that Latino siblings of children with MR/DD will report more positive sibling relationship quality and more family obligations. We predict that familistic cultural values will be associated with higher rates of internalizing symptoms and psychopathology, and moderated by social support. Participants: 200 healthy 8-13 year old siblings in 4 groups will participate based on a 2 X 2 (Latino v. nonLatino X MR/DD v. typical) design. Method: Participants will complete measures of sociodemographics, characteristics of the sibling (age, sex, birth order, pubertal status), child with MR/DD (screen of intelligence, maladaptive behavior), parent mental health, culture (acculturation, immigration, familistic values), and social support, as predictors of sibling psychological and somatic symptoms, psychopathology, sibling relationship quality, sibling family obligations, and school and social functioning. Analyses: Correlations, analyses of variance and covariance, and hierarchical multiple regressions will be used to analyze data. Significance: Latino siblings of children with MR/DD are at risk for significant unrecognized and untreated psychological problems that could lead to long-term impairment. The results of this study will increase our understanding of the mental health needs of Latino children and provide information essential for developing culturally appropriate interventions. [unreadable] [unreadable] [unreadable]